Heretofore, various efforts have been made to provide automatic exhaust stack damper controls. Illustrations of this are found in the following Patents:
______________________________________ PATENTS ISSUED TO ______________________________________ 352,874 Johnson 684,270 Kornreich 859,375 Ehlers 1,591,228 Obenhaus et al 2,856,922 Bartels 2,946,554 Asker et al 3,010,451 Holzman et al 3,273,625 Holzman et al 66,582 1/1929 - Norway 3,580,238 Diehl 2,977,437 Doane. ______________________________________
The disadvantage of most of these patent disclosures was that the devices are complicated or unsafe or impractical.